title: Spectral properties of fluorescence induced by glutaraldehyde fixation.
abstract: Following fixation with glutaraldehyde, tissues or gelatin films fluoresce. This fluorescence can be enhanced more than thirtyfold by several minutes exposure to near ultraviolet light. Longer wavelengths produce a smaller effect. The enhanced fluorescence is maximally excited at 540 nm (half-band width about 45 nm), and fluorescence emission peaks at 560 nm. The rate of photoenhancement is independent of temperature in the 12--30 degrees C range. Photoenhancement is greater at alkaline than acid pH; the pH dependence involves a single acid binding group with pK = 7.3. These effects are not observed following treatment with paraformaldehyde or prior reduction with boranedimethylamine. Schiff base linkages between the bifunctional cross-linking reagent and free amino groups therefore seem to be involved. The effects of pH and wavelength on the photoenhancement of fluorescence are best accounted for by a kinetic scheme that includes both photogeneration of fluorophore from an ultraviolet-absorbing precursor, and its subsequent photodestruction by visible light.
mesh_terms: D000447:Aldehydes; D000818:Animals; D003400:Astacoidea; D002462:Cell Membrane / Q000648:ultrastructure*; D005976:Glutaral; D007202:Indicators and Reagents; D008856:Microscopy, Fluorescence / Q000379:methods*; D008871:Microvilli / Q000648:ultrastructure*; D014466:Ultraviolet Rays
chemical_list: D000447:Aldehydes; D007202:Indicators and Reagents; D005976:Glutaral